Modern climate science is based on facts, physics and testable hypotheses. There is ample room for debate about what to do about climate change, but the underlying science is rock solid.

Modern climate science builds on a long track record of scientific inquiry on environmental and health issues that has benefited society. Through scientific analysis, it was discovered that DDT, widely used as a pesticide, was becoming concentrated in the food chain. As a result, laws were passed to curb its use. Tetraethyl lead was once added to gasoline to reduce engine knock. Through science, we learned that lead in the environment poses severe health hazards, so the use of lead in gasoline was consequently phased out. It was through science that we learned how CFCs were destroying stratosphere ozone. In turn, through many decades of research, we have developed a strong understanding of how the climate system works, how humans are affecting climate, and what is in store if society continues to follow its current path without taking corrective action.

Until the middle off the 20th century, climate science was pretty much a backwater. Climatologists, by and large, were bookkeepers, compiling records of temperature, precipitation and other variables. From these records, much effort was spent classifying climate types around the world, ranging from tropical rain forests to monsoons to semiarid steppes to deserts. Climate data certainly had value to farmers and the home gardener, civil and structural engineers and the military planning. But the focus was largely on statistics, with relatively little emphasis on climate dynamics – the processes that control the climate system and how it may evolve. There were notable exceptions, such as Svante Arrhenius, who, in the late 19th century, speculated on how rising concentrations of carbon dioxide would lead to warming, but for the most part, climatology was a largely descriptive and rather boring field of science.

The shift from simple bookkeeping to a more physically-based view of how the climate system works paralleled developments in meteorology—the science of weather prediction. The rapid advances in meteorology following the Second World War, in turn, largely paralleled the development of numerical computers. With computers, it became possible to translate the physical processes controlling weather systems into computer code. It was readily understood that the physics controlling weather were part of the broader set of physics that control climate, which led to the development of global climate models, or GCMs for short. GCMs were quickly seen as powerful tools to understand not just how the global climate system works, but how climate could change in response to things like brightening the sun or altering the level of greenhouse gases in the atmosphere.

Using early generation GCMs developed in the 1970, pioneers like Jim Hansen of NASA, and Suki Manabe of the Geophysical Fluid Dynamics Laboratory in Princeton confidently predicted that our planet was going to warm up, and that the Arctic would warm up the most, something that we now call Arctic amplification. But the more mundane chore of compiling climate records never stopped, and indeed, its value grew, for it was only with ever-lengthening climate records that it could be determined if things were actually changing. And as these records grew, it slowly became clear that the planet was indeed warming. From numerous GCM experiments, it also became clear that this warming, and all the things that go with it, such as the Arctic’s shrinking sea ice cover and Artic amplification, could only be explained as a response to rising levels of carbon dioxide in the atmosphere.

Climate scientists of today need to know:

The processes that can change how the earth absorbs and emits energy

How the atmosphere and weather systems work

How the atmosphere interacts with the oceans

How the atmosphere interacts with the land surface

And how the land interactions with the ocean.

But whatever our area of specialty, we all try and make contributions to our understanding, but those contributions are, to the best of our ability, based on facts, physics, and sound methodology. In science, there is no room for wishful thinking. As a society, need to get past partisan bickering, step back, and listen to what climate science is telling us: the climate is changing, we know why, and the implications must not be ignored. This is the value of climate science.

Mark C. Serreze is director of the National Snow and Ice Data Center, professor of geography, and a fellow of the Cooperative Institute for Research in Environmental Sciences at the University of Colorado at Boulder. He is the coauthor of The Arctic Climate System. He lives in Boulder, Colorado.

In the 1990s, researchers in the Arctic noticed that floating summer sea ice had begun receding. This was accompanied by shifts in ocean circulation and unexpected changes in weather patterns throughout the world. The Arctic’s perennially frozen ground, known as permafrost, was warming, and treeless tundra was being overtaken by shrubs. What was going on? Brave New Arctic is Mark Serreze’s riveting firsthand account of how scientists from around the globe came together to find answers. A gripping scientific adventure story, Brave New Arctic shows how the Arctic’s extraordinary transformation serves as a harbinger of things to come if we fail to meet the challenge posed by a warming Earth.

Why should we care about what is going on in the Arctic?

The Arctic is raising a red flag. The region is warming twice as fast as the globe as a whole. The Arctic Ocean is quickly losing its summer sea ice cover, permafrost is thawing, glaciers are retreating, and the Greenland ice sheet is beginning to melt down. The Arctic is telling us that climate change is not something out there in some vague future. It is telling us that it is here and now, and in a big way. We long suspected that as the climate warms, the Arctic would be leading the way, and this is exactly what has happened.

There are a lot of books out there on the topic of climate change. What makes this one different and worth reading?

I wanted to get across how science is actually done. Scientists are trained to think like detectives, looking for evidence, tracking down clues, and playing on hunches. We work together to build knowledge, and stand on the shoulders of those who came before us. It a noble enterprise, but a very human one as well. We sometimes make mistakes (I’ve made a few doozies in my time) and get off the rails. Too often, science gets twisted up with politics. I tell it like it is, as a climate scientist who was there back when the Arctic was just beginning to stir, and both watched and participated in the story of the changing north.

You’ve hinted about how growing up in Maine got you interested in snow and ice. Can you tell us a little about this?

I grew up in coastal Maine in the 1960s and 1970s when there were some pretty impressive winters. Winter was my favorite season. I was way into daredevil sledding, and spent countless hours building the iciest, slickest track possible and modifying my sled for maximum speed. I developed a reputation for building tremendous snow forts with five or six rooms connected by tunnels. We’d would go crawling through the tunnels at night and light candles in each room. Then there was the simple primal joy of watching a big Nor’easter snowstorm come through and grind commerce to halt. The craziest winter activity I got into with my sister Mary and friend Dave was riding ice floes on the Kennebunk River. I probably should have drowned several times over, but, in retrospect, I learned a lot about the behavior of floating ice. Now, this was all back in an era when most of us were free-range kids—my mom would say, “get out of the house, I don’t want to see you ‘til dinner.” So you made your own fun and it wasn’t always safe. But it prepared me very well for a career studying snow and ice.

It took you quite a few years to be convinced of a human role in climate change. Why so long?

As mentioned, scientists are detectives, and we are always weighing the evidence. For me, it was never a question of if we would eventually see the human imprint of climate change in the Arctic—the basic physics behind greenhouse warming had been understood as far back as the late 19th century. Rather, it was a question of whether the evidence was solid enough to say that the imprint had actually emerged. The challenge we were up against is that natural variability is quite strong in the Arctic, the system is very complex, and most of the climate records we had were rather short. By the late 1990s, it was clear that we were seeing big changes, but at least to me, a lot of it still looked like natural variability. It was around the year 2002 or 2003 that the evidence became so overwhelming that I had to turn. So, I was a fence sitter for a long time on the issue of climate change, but that is how science should work. We are trained to be skeptical.

What happened in the year 2007? Can you summarize?

In the early summer of 2007, sea ice extent was below average, but this didn’t really grab anyone’s attention. That quickly changed when ice started disappearing at a pace never seen before. Through July and August, it seemed that the entire Arctic sea ice community was watching the daily satellite images with a growing sense of awe and foreboding. Huge chunks of the ice were getting eaten away. By the middle of September, when it was all over, the old record low for sea ice hadn’t just been beaten, it had been blown away. There was no longer any doubt that a Brave New Arctic was upon us. Arctic climate science was never really the same after that.

We keep hearing about how science tends to be a male-dominated field. But the impression that one gets from your book is that this isn’t really the case in climate research. Can you comment?

I don’t know what the actual numbers look like in climate science versus, say, computer science, but in my experience, when it comes climate research, nobody really cares about your gender. What’s important is what you know and what you can contribute. What you do see, certainly, is more female graduate students now coming through the system in STEM fields (Science, Technology, Education, Mathematics).

Are you frustrated by the general inaction, at least in the United States, to deal with climate change?

I’m constantly amazed that we don’t take the issue of climate change more seriously in this country. We are adding greenhouse gases to the air. The climate is warming as a result. The physics are well understood. Just as expected, the Arctic is leading the way. Sure, there are uncertainties regarding just how warm it well get, how much sea level will rise, and changes in extreme events, but we know plenty about what is happening and where we are headed. The costs of inaction are going to far outweigh the costs of addressing this issue.

Mark C. Serreze is director of the National Snow and Ice Data Center, professor of geography, and a fellow of the Cooperative Institute for Research in Environmental Sciences at the University of Colorado at Boulder. He is the coauthor of The Arctic Climate System. He lives in Boulder, Colorado.

In honor of Earth Day, Princeton University Press will be highlighting the contributions that scientists make to our understanding of the world around us through a series of blog posts written by some of our notable Earth Science authors. Keep a look out for this series all month long.

Mark Serreze, investigating the pressure ridges in the Arctic.

What is it that leads someone to become a scientist? It varies, but from what I’ve seen, it’s often a combination of nature and nurture. Just as some people seem to have an inherent knack for writing making music, or cooking, I think that some of us are wired to become scientists. In turn, there is often someone we can look back to—parents or perhaps a teacher—that encouraged or inspired us to pursue a science career.

I had an interest in science from when I was very young, and I was always full of questions about the natural world. The first book I ever owned is “The Golden Book of Science” 1963 edition—featuring 1-2 page essays on everything from geology to insects to the weather. Each night, at my insistence, my mother would read one of them to me. To this day, I still own the book.

When I wasn’t reading, I could spend hours outside marveling at the organized industriousness of ants as they built their anthills, or looking at colorful rocks with a magnifying glass. I was enthralled with the burgeoning manned space flight program, and, sitting beside my mother and staring at the black TV while she ironed clothes, watched in awe at the Project Gemini rocket launches.

As for the nurture part, I had an advantage in that both of my parents were chemists with Master’s degrees. This was at a time it was quite unusual for women to hold advanced degrees. They met in the laboratory. Mom was a whiz when it came to thermodynamics, and Dad apparently knew everything there was to know about acrylic plastics. Ours was indeed an odd household. While my siblings and I chafed under a rather strict Catholic upbringing, at the same time we were very much free-range kids, and scientific experimentation of all sorts was quite acceptable.

At one point, after getting a chemistry set for Christmas, I thought I might become a chemist myself. These were not the boring, defanged chemistry sets of today – back then, they included chemicals that, when properly mixed, yielded career-inspiring reactions. I later got heavily into model rocketry, astronomy, and civil engineering, building small dams across the stream running past our house to improve the habitat for the frogs. Included among the more foolish (albeit highly educational) endeavors was a scientifically-based experiment on the feasibility of riding ice floes down the Kennebunk River. Then there was the time when an experiment in pyrotechnics gone wrong ended up with a frantic call to the fire department to douse a five-acre conflagration in the neighbor’s field.

Years before I ever got into college I knew I was going to be a research scientists of some type, for, through nature and nurture, the roots were already there. As I talk about in my book, Brave New Arctic, a number decisions and events came together – mixed with some blind, dumb luck – to eventually steer me towards a career in climate science. What I could never have foreseen is how, through these events and decisions, and then through 35 years of research, I’d find myself in the position to tell the story about the dramatic transformation of the North.

Climate scientists, like myself, have to deal with an added challenge that climate change is a highly polarized subject. There are the frequent questions from the media: Will there be a new record low in Arctic sea ice extent this year? Why does it matter? Why is the Arctic behaving so differently than the Antarctic? It can be overwhelming at times. Then there are the emails, phone calls and tweets from those who simply want to rant. While I get a lot of emails from people fully on board with the reality that humans are changing the climate and want to get straight answers about something they’ve heard or read about, I also have a growing folder in my inbox labeled “Hate Mail”. Some very unflattering things have been said about me on social media and across the web. I’ve had to grow a thick skin.

Making a career as a research scientist is not for everyone. Science is not the sort of thing that is easy to put aside at the end of the day. It gnaws at you. The hours are long, and seldom lead to monetary riches. It can also be a frustrating occupation, such as when realizing that, after months of research pursuing a lead, you’ve hit a dead end.

We chose to be scientists because it’s what we love to do. We live for those “aha” moments when the hard work pays off, and we discover something new that advances our understanding.

In writing this book I was forced to dig deeply to understand my own evolution as a scientist, and to document insights from other scientists who, like me, were there at the beginning when the Arctic still looked like the Arctic of old. It’s been an adventure, and when I someday retire (which is a very hard thing for scientists to do,) I hope to be able to look back and say that that this book opened some eyes, and inspired others to follow their own path to becoming a scientist.

Mark Serreze is director of the National Snow and Ice Data Center, professor of geography, and a fellow of the Cooperative Institute for Research in Environmental Sciences at the University of Colorado at Boulder. He is the coauthor of The Arctic Climate System. He lives in Boulder, Colorado.

The floating sea ice atop the Arctic Ocean waxes and wanes with the seasons. The maximum extent typically occurs around the second week of March, at which time ice has historically covered an area a bit less than twice the size of the contiguous United States. The term “Arctic sea ice extent” is actually a bit of a misnomer, for at or near the seasonal maximum, sea ice is found well south of the Arctic Circle, covering all of Hudson Bay and parts of the Bering Sea, the Sea of Okhotsk, the Baltic Sea and the Gulf of St. Lawrence. With the start of spring, the ice cover begins to melt. Initially, the growing warmth of spring slowly nibbles away at the southern edges of the ice pack. The pace of melt picks up in May and June, and then gets underway in earnest in July. As the sun gets lower in the sky in August, the melt slows. The seasonal minimum in ice extent usually occurs in mid-September – at that time, the ice covers less than half of what it did in March, and ice is restricted to the Arctic Ocean proper. As the sun then sets over the Arctic Ocean, the ice cover begins to grow again, renewing the cycle that has been going on for millions of years.

But things are changing fast. Earth observation satellites have been recording changes in Arctic sea ice extent since 1979. These records show that sea ice extent is declining in all months, with the largest change in September, at the end of the melt season. The downward trend for September is a whopping 13% per decade. The trends are by no means smooth – there are big ups and downs from month to month and year to year, but the pattern is clear.

Scientists have long been at work to determine what sea ice conditions were like before the satellite era. Data from shore observations, ship and aircraft reports, and before aviation, sources like logbook entries from whaling ships, extend the record back to 1850. Paleoclimate reconstructions bring the record back a thousand years before today. There is no evidence in any of these records for sea ice trends like we’ve seen over the past 40 years. They are unprecedented. The conclusion is inescapable – the Arctic Ocean is quickly losing its floating sea ice cover. The summer ice cover may be gone 30 or 40 years from now.

At the University of Colorado National Snow and Ice Center (NSIDC), where I’ve been the director since 2009, we track the Arctic sea ice cover on a daily basis. Every August, we start to brace ourselves for the inevitable tidal wave of questions from the media and interested public about what September will bring. Questions like: Will there be a new record low in sea ice extent this year? When will the Arctic completely lose its summer sea ice cover? What will this mean for the rest of the planet? We also get our share of flak from the skeptics, eager to tell us that this is all some sort of natural climate cycle, or that nothing is happening at all; we’re making it up and fudging the records. We shrug this off and diligently continue processing the satellite data and report on what is happening. The data does not lie.

Until a few years ago, the March sea ice maximum went relatively unnoticed. By comparison to September, the changes being seen in winter weren’t especially spectacular, and for good reason – even in a warming Arctic, it still gets cold and dark in winter and sea ice forms and covers a big area. The ice that grows in autumn and winter is thinner than it used to be, but to the satellite sensors that we use to determine ice extent, thin ice looks pretty much the same as thick ice.

Things changed in 2015, when sea ice extent at the March maximum set a new record low. Then the winter of 2015-2016 saw a mind-boggling heat wave over the Arctic Ocean. At the end of December 2015, there was a brief period when the surface temperature at the North Pole rose to the melting point. In all my years of studying the Arctic, I’d never seen anything like it. It stayed warm and on March 24, when Arctic sea ice reached its seasonal maximum extent, it had bested the low mark set in 2015. The winter of 2016/2017 was in many respects a repeat. At the winter solstice on Dec. 22, temperatures near the North Pole were up 20 degrees Celsius (35 degrees Fahrenheit) above average. When March 2017 rolled around, another new record low in extent had been set. The Arctic has gone crazy.

We’re still coming to grips with understanding these records lows in the winter ice cover. While the heat waves are clearly related to weather patterns bringing in warm air from the south, what’s the cause of these patterns? While more ocean heat seems to be coming into the Arctic Ocean from the Pacific through the Bering Strait, why is this happening? The inflow of ocean heat from the Atlantic has also changed in puzzling ways that inhibit winter ice formation in places like the Barents Sea.

In short, while we know a great deal about what is happening to the Arctic and where it is headed, the emerging Brave New Arctic continues to challenge us. Maybe we shouldn’t be all that surprised – after all, scientists have long known that, as the climate warms, the biggest changes would be seen the Arctic. That doesn’t mean that we can’t be amazed.

Mark C. Serreze is is director of the National Snow and Ice Data Center, professor of geography, and a fellow of the Cooperative Institute for Research in Environmental Sciences at the University of Colorado at Boulder. He lives in Boulder, Colorado.

In the 1990s, researchers in the Arctic noticed that floating summer sea ice had begun receding. This was accompanied by shifts in ocean circulation and unexpected changes in weather patterns throughout the world. The Arctic’s perennially frozen ground, known as permafrost, was warming, and treeless tundra was being overtaken by shrubs. What was going on? Brave New Arctic is Mark Serreze’s riveting firsthand account of how scientists from around the globe came together to find answers.

Mark C. Serreze is director of the National Snow and Ice Data Center, professor of geography, and a fellow of the Cooperative Institute for Research in Environmental Sciences at the University of Colorado at Boulder. He is the coauthor of The Arctic Climate System. He lives in Boulder, Colorado.

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